The 8800nl does not support G.Vectoring ( G.993.5) according to the compliance list, unless it's just not enabled in the current firmware
Full-rate ANSI T1.413 Issue 2
G.993.2 (VDSL2, supporting profile 8a, 8b, 8c, 8d, 12a, 12b, 17a)
G.992.1 (G.dmt)
G.992.2 (G.lite)
G.992.3 (G.dmt.bis)
G.992.3 Annex M (ADSL2 Annex M)
G.992.4 (G.lite.bis)
G.992.5 (G.dmt.bis plus)
G.992.5 Annex M (ADSL2+ Annex M)
G.994.1 (G.hs)
VDSL2 band plan: 997 and 998
I was told that BT are currently using the device in tests but wouldn't confirm if that included vectoring support.